Control apparatus



March 9, 1965 R. l.. RICHARDS CONTROL APPARATUS 3 Sheets-Sheet l Filed April 28, 1961 www IN VENTOR ROBERT L. RICHARDS March 9, 1965 R. 1 RICHARDS CONTROL APPARATUS 3 Sheets-Sheet 2 Filed April 2s, 1961 .llo# foo l'. n@ N MT om WMV 3 www HQI .vdi

INVENTOR ROBERT L.R|cHARos March 9, 1965 R. RICHARDS CONTROL APPARATUS 3 Sheets-Sheet 3 Filed April 28 1961 NJI n@ www ma l||||||||| )Jlllm augen .EOC

INVENTOR ROBERT L.R|CHARO$ United States Patent O 3,l73,tl58 CONTRUL APPARATUS Robert L. Richards, Media, Pa., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 28, 1961, Ser. No. 106,259 lil Claims. (Cl. 317-6l This invention relates to apparatus for sensing the inphase relationship of a pair of rotatable shafts. The inphase relationship may bel defined as a rotative position of one shaft that substantially coincides with the rotative position of the other shaft.

One of the main objects of the invention is to provide apparatus of the above type in which the irl-phase sensing means provides an electrical signal that may be employed to automatically initiate a control function.

Another object is to provide apparatus of the above type for sensing the iii-phase relationship of two slowly rotating turbine-generator rotors and automatically initiating a subsequent function. The subsequent function may, for example, include the simultaneous application of DC. excitation voltage to the field coils of both generators to electrically interlock or synchronize the two generator rotors before bringing them up to rated speed.

During initial startup of a turbine power plant, the turbine-generator rotor is slowly rotated at a speed ranging from 3 to 30 rpm. by a motor driven turning gear mechanism for reasons well known in the art.

In cross-compound connected power plants which include a first turbineagenerator unit and a second turbinegenerator unit driven by turbines at different pressures, for example, a high pressure and a low pressure, both unit are initially slowly rotated by individual turning gear mechanism and, during this slow speed rotation, the two units are electrically interconnected by simultaneously applying D.C. excitation voltage to the field coils of both generators. The turbineenerator rotors are then jointly brought up to speed by admission of pressurized elastic motive fluid such as steam. Before the DC. voltage may be safely applied to both generator field coils, it is essenial that the two turbine-generator rotors be in-phase with each other.

l-leretofore, many schemes have been employed for visually detecting the in-phase relationship of the two rotors by an operator in order to enable him to decide the proper instant for applying the excitation voltage. Such arrangements have heretofore been employed with varying degrees of success, depending upon the skill and experience of the operator.

However, with the advent of automation in steam turbinegenerator power plants, it is desirable to sense the iii-phase relationship of the two turbine-generator rotors and subsequently automatically apply the DC. field excitation voltage to the generator field coils. ln addition to the above automatic function, it is also desirable to initiate other associated functions and operations incidental to starting the turbine-generator power plant and bringing it up to rated speed. For example, it is desirable to provide ay signal to ay computer mechanism indicative of excitation of the eld coils and synchronization of the two turbine-generator rotors, so that the computer mechanism may initiate or monitor the functions of related auxiliary and/ or control devices, aswell known in the art.

Briefly, in accordance with the invention, there is pro` vided a balanced electrical bridge circuit having a lirst pair of serially connected legs and a second pair of serially connected legs, each of the legs including one electrical impedance member. The impedance members are arranged in two pairs, each pair including a xed impedance member and a variable impedance member. Means such 3,173,058 Patented Mar. 9, 1965 ICC as an electrical relay coil interconnected between the rst pair of legs and the second pair of legs is further provided for sensing the condition of balance and unbalance in the bridge circuit. The first pair of impedance members `are disposed in radially spaced relation with a shaft portion of the high pressure turbine-generator rotor, while the second pair of impedance members are disposed in similarly radially spaced relation with a shaft portion of the low pressure turbine-generator rotor. The two shafts are of substantially circular cross section so that, during rotation, the air gaps between the shafts and the associated fixed impedance members are maintained substantially constant. However, that portion of each shaft which rotates past the variable impedance members is provided with an axially elongated recess (or projection) arranged with reference to the poles of its generator rotor. Hence, when the two rotors are in phase, the two recesses are disposed in the same rotative positions relative to each other. During rotation, the air gaps between the shafts and their associated variable impedance members remains unchanged except during the brief time interval that the recesses are disposed in alignment with their associated variable impedance members.

The two variable impedance members are disposed in the diametrically opposed legs of the bridge circuit. Hence, when only one of the recesses is disposed in registry with its associated variable impedance member the bridge becomes partially unbalanced and the voltage drop across the relay coil is insutiicient to actuate the relay. However, when both recesses are disposed in registry with their associated variable impedance members `at the same time, the first pair of serially connected legs becomes unbalanced in one direction while the second pair of serially connected legs become unbalanced in the opposite direction. The voltage drop across the relay coil at this time is equal to twice the imbalance `attained in each pair of serially connected legs. The potential thus impressed across the relay coil is eifective to actuate the relayv which, in turn, is effective to connect a source of D.C. voltage to the field coils of the two generators, thereby electrically interlocking the two rotors and insuring that they are jointly brought up to rated speed upon application of motive fluid to the turbines. ri`he relay may further be provided with additional contacts to complete a circuit to a computer or monitoring device and/or a visible signal device such as a lamp.

With the above arrangement, the irl-phase relationship of the two shafts is detected when they are in only one iti-phase position. Hence, the iii-phase condition may not be detected for a considerable period of time, even though the two shafts attain the irl-phase relationship in other rotative positions. To increase the probability of detecting iii-phase relationship in a shorter period of time, a plurality of electrical bridge circuits of the above type may be employed; each, having the same arrangement of fixed and variable impedance members as above. However, in this arrangement, the variable impedance mem.- bers are disposed in an annular spaced array about their associated shafts. For example, if four bridge circuits are employed, the variable impedance members in the first pairs of serially connected legs may be disposed at l2, 3, 6 and 9 oclock on one shaft, while the variable impedance members in the second pairs of serially con: nected legs may be similarly disposed about the second shaft.

rlhe above and other objects are effected by the invention as will be apparent from the following description taken in connection with the accompanying drawings,l forming a part of ythis application, in which:

FIG. l is a highly diagrammatic view illustrating one embodiment of the invention, in yco'nr'rection with a cross compound turbinegenerator power plant;

FIG. 2 is an enlarged sectional View taken on line II- II of FIG. l;

FIG. 3 is an axial section taken on line III-III of FIG. 2;

FIG. 4 is a schematic electrical diagram illustrating the bridge circuit (and associated electrical apparatus arranged in accordance with the invention;

FIGS. 5 and 5A are views showing representative voltage drops attained in the bridge circuit when the two shafts are disposed in one possible relative position;

FIGS. 6 and 6A, and FIGS. 7 and 7A are views similar to FIGS. 5 and 5A, respectively, but showing representative voltage drops attainable in the bridge circuit when the two shafts are disposed in other possible relative positions;

FGS. 8 and 8A are views similar to FIGS. 5 and 5A, respectively, but showing representative voltage drops attained in the bridge circuit when the two shafts are in phase with each other;

FIG. 9 is a sectional view taken on line iX-IX of FIG. 10 and similar to FIG. 2 but showing another embodiment of the invention;

FIG. 10 is a view taken on line X-X of FlG. 9;

EG. 11 is a schematic electrical diagram illustrating the circuitry employed in the second embodiment;

FIG. 12 is 'a schematic view of one of the bridge circuits employed with the second embodiment and showing representative voltage drops attained in the bridge under one set of conditions; and

FIG. 13 is a diagram similar to FIG. 12 but illustrating representative voltage drops when the two shafts are in an in-phase position detectable by one of the bridge circuits.

Referring Ato the drawings in detail, in FIG. 1 there is shown a turbine-generator power plant 1d of the crosscompound type including a high pressure turbine lll drivingly connected to an electrical generator 12 by a shaft 1.3, and a low pressure turbine 14 drivingly connected to an electric generator Iby a shaft 16. The generator 12 is provided with a rotor 17 having an extended shaft portion 18 carrying a pair of slip rings lljl connected to the lield coils 2d* of the lgenerator 3.2. In a similar manner, the generator is provided with a rotor 2l having an extended shaft portion 22 carrying a pair of slip rings 23 connected to the lield coils 24 of the `generator 15.

The turbine-generator unit 1l, i2 is provided with a motor opera-ted turning gear mechanism 26 for jointly rotating the generator rotor 17 and the turbine rotor (not shown) at a slow speed for reasons well known in the art. In a similar manner, the turbine-generator unit i4, 15 is provided with motor operated turning gear mechanism 28 for slowly rotating the generator rotor Ell and the turbine rotor (not shown). The high pressure turbine 11 is provided with a steam inlet 3@ and a steam outlet 31. Likewise, the low pressure turbine 14 is provided with a steam inlet 32 and a steam outlet 33. High pressure steam is supplied from a suitable source (not shown) to the steam inlet 30 and is expanded in the turbine 11 to motivate the same subsequent exhaustion through the outlet 31. After the ste-am is exhausted through the outlet 3l, it is directed to the steam inlet 32 of the low pressure turbine 14 by a conduit indicated at 34. The steam undergoes additional expansion in the low pressure turbine to motivate the same before subsequent exhaustion through the outlet 33.

The turning gear mechanisms Z6 and Z8 are arranged to drive the associated shafts i3 and 16, respectively, at slightly different speeds. Hence, during rslow speed rotation of the two turbine generators, the two shaft portions 18 tand 22 periodically attain an in-phase relation with respect to each other. By referring to FG. 2, it will be noted that the generator rotors 17 and 21 are of the two pole type, each having a north pole N and a south pole S. As shown in FIG. 2, the generator rotors 17 and 21 are in-phase. That is, their north and south i poles are disposed in the same rotative position relative to each other.

A motor driven D C. generator 36 is employed to provide D.C. excitation voltage to the field coils 24 through a pair of electrical conductors 37 having interposed therein an electrically actuated circuit breaker mechanism 38. The conductors 37 are disposed in suitable slidable contact with the slip rings 23. Also, a motor driven D.C. generator itl is employed to provide D.C. excitation voltage to the held coils 20 through a pair of suitable conductors il disposed in slidable Contact with the slip rings t9 and having interposed therein an electrically actuated circuit breaker 42.

When it is determined that the two generator rotors ll7 and Zll are in-phase, the circuit breakers 3S and 42 are jointly energized, thereby electrically exciting the lield coils TA and 20, respectively. Hence, as well understood in the art, the two generators are electrically synchonized or interlocked and will subsequently rotate at precisely the same speed. After synchronization of the two generators, motive steam is applied to the turbines l1 and ld and the turning gear mechanisms 26 and 2S are disengaged. The generators are then brought up to rated speed by the turbines. Thereafter, control of the power plant itl may be attained in any suitable manner (not shown).

As thus far described, the apparatus is substantially conventional and requires visual detection of the in-phase relationship of the two shafts .1.8 and 2,2 and manual operation of the two circuit breakers 38 and 42.

In accordance with the invention, there is provided apparatus, generally designated d5, for automatically detecting the irl-phase relation of the two shafts llt; and 22 and for jointly automatically actuating the circuit breakers 3S and 42.

The apparatus d5, as best shown in FIG. 4, comprises an electrical bridge circuit t6 having a rst pair of serially connected legs 47 and 4S and a second pair of serially connected legs d@ and 5t?. The first pair of legs 47, 46 and the second pair of legs 49, 50 are interconnected at their midpoints Si and 52 and suitable voltage is applied to the connections S3 and 54 from a power supply (not shown) by lines L1, L2. The voltage may be either A.C. or DC. and is preferably regulated by a suitable voltage regulator 55. The power supply thereto may be controlled by a suitable switch 56. It will now be seen that the bridge circuit 46 is substantially of the Wheatstone type.

A pair of variable impedance members A1 and A2 are disposed, respectively, in the diametrically opposed bridge legs 47 and 50, while a pair of fixed reference impedance members R are disposed in the diametrically opposed bridge legs t8 and 49. The impedance members A1, A2 and R are ofsubstantially identical impedance characteristics. Hence, the bridge circuit i6 is inherently balanced, since the impedance ratio.

A1 R (leg 49) R (leg as) A, This may better be understood by stating that the voltage drop across A1 is equal to the voltage drop across R in leg 48, while the voltage drop across R in leg 49 is equal to the voltage drop across A2. With the bridge in the thus balanced position, the potential across the interconnecting points 51 and 52 is zero.

Referring again to FiG. 1, the variable impedance member A1 and its associated fixed impedance member R are disposed in equally radially spaced relation with the shaft i8, while the variable impedance member A2 and its associated xed impedance member R are disposed in equally radially' spaced relation with the shaft 22. The cross sectional shape of the two shafts ll and 22 in the region disposed adjacent the iixed impedance members R is substantially cylindrical so that, regardless of the rotative positions of the shafts, the air gaps formed bearr/aces il tween the fixed impedance members and their' associating shafts is constant or unchangeable. That portion of the shaft l@ disposed adjacent to and rotating past the variable impedance member A1 is also of cylindrical shape but has an axially elongated recess E58 formed therein. Hence, during rotation of the shaft the air gap formed between the variable impedance member A1 and the shaft is substantially constant through all portions of travel of the shaft therepast with the exception that, when the recess 58 is disposed in radial alignment with the variable impedance member A1, the length of the air gap is suddenly increased with attendant decrease in impedance of the variable impedance A1. ln a similar manner, the shaft 22 is provided with an elongated recess 59 for varying the impedance of the variable impedance member A2. As illustrated in FIG. 2, the recesses 58 and 59 are disposed in radial alignment with the north poles N ot their respective rotors ig' and 2i.

An electrical relay di having an inductive winding or coil d2 aording the interconnection between points Si. and 52 of the bridge is employed to control the actuation of the two circuit breakers 3S and ln addition there to, the relay til may further be employed to provide a signal to an electronic computer or monitoring device 63 and an electrical signalling member such as a lamp dit.

rThe relay dll may be oi any suitable multiple contact type. However, for illustration purposes it has been shown as having a magnetic core member du slidably received within the inductive winding d2 and having an elongated rod structure o7 carrying a plurality or" bridging contacts ed, @9, itl and 7l arranged in suitably insulated relation with each other. Each of the bridging contacts d8, d5, 7i? and il is cooperatively associated with a pair of stationary contacts '72, 73, '74 and '75, respectively, arranged in such a manner that when the relay is in the deenergized position all of the contacts are disengaged.

T 1e relay contacts 6b and i2 are arranged to complete a circuit from the power supply lines L1, L2 through the circuit breaker 3S; tl e elay contacts o9 and 73 are arranged to complete a circuit from the lines L1, L2 through the circuit breaker 42; and the relay contacts 7'@ and 7d are arranged to complete a circuit from the lines L1, L2 through the signal lamp ed. The contacts and 7S are arranged to energize a holding circuit through the computer 63, which circuit includes a electrical relay, generally indicated 76, having an inductive winding 77 within which is slidably received a magnetic core 78. A rod member 79 is attached to the core '7S and is provided with a pair of bridging contacts Si and S2 disposed in insulated relationship with each other. The relay 7rd is also ot' the normally open type and further includes a pair of stationary contacts S3 cooperatively associated with the bridging contact bl and a pair of stationary contacts cooperatively associated with the bridging contact 82. The left-hand stationary contact is connected to the winding 77 by a conductor S5 disposed in parallel with a conductor S6 which, in turn, connects the winding 7?' with the let hand stationary Contact '75. The other end of the winding 77 is connected to line L1 of the power supply by a conductor 87, while right-hand contacts 9,3 and 75 are connected to the other line L2 by conductors b9 and 90, respectively.

The impedance members A1, A2 and R may be of any suitable type. For example, their reactance may be either inductive or capacitive. However, as illustrated in FlG. 3, wherein impedance members A1 and R in bridge legs /t' and le are shown, they are of the inductive type typically comprising an iE-shaped magnetic armature 31. having three legs extending toward the associated generator shaft i8 and having an inductive coil 92 formed about the central le". As well known in the art, when the coil 92 is energized with AC. current it induces a magnetic eld in the armature 91 which ex- CTR tends across the air gap 93 formed between the ends ot the legs and the surface of the rotatable shaft 18. The shaft lil completes the magnetic circuit. As well known in the art, as the length of the air gap is increased, the magnetic reluctance of the magnetic circuit is increased, thereby reducing the inductive reactance of the impedance member thereby reducing the voltage drop across the impedance member.

Since the impedance member R is disposed adjacent the cylindrical portion of the shaft T18, its air gap 93 is maintained constant and therefore its impedance is held to a constant value. Although the variable impedance member A1 may be structurally identical to the impe/lance member R, it is disposed in the region of the shatt lil having the recess 58 formed therein. Hence, during all rotating positions of the shaft 1b, except for the brief period of time when the slot 5b is disposed immediately opposite the legs of the armature 91, the impedance of the impedance member A1 is constant and substantially identical to that ot the impedance member R. However, when the slot Sti is in alignment with the armature 9l of the member A1, the air gap is suddenly increased in length with a concomitant increase in magnetic reluctance of the magnetic circuit and and reduction in the inductive reactance of the impedance member A1, thereby reducing the voltage drop across the impedance member A1. From the above, it will now be seen that when the shaft i8 and the impedance members R and A1 are relatively disposed in the position shown in FG. 3, the voltage drop X across impedance member R is equal to the voltage drop Y across the impedance member A1.

Reterring to FIG. 5A, it will be noted that the positions of the shafts l@ and 22 with relation to their associated variable impedance members A1 and A2, respectively, is such that neither of the slots 58 and 59 are disposed in alignment with their associated variable impedance members. With the shafts in this position and assuming the voltage across lines L1, L2 to be 100 volts AC., by referring to FlG. 5 it will be noted that the voltage drop across each of the legs of the bridge 46 is 5) volts and the bridge is in a substantially balanced condition. Accordingly, the voltage drop across the relay winding d2, is O volts and the relay 6l is in the deenergized or open position (as shown in FIG. 4).

Referring to FIG. 6A, it will be noted that the recess 58 is disposed in alignment with the variable impedance member A1, so that the voltage drop thereacross is reduced while the voltage drop across the impedance member A2 is normal. By referring to FIG. 6, it will be seen that the bric ge is now in a partially unbalanced position. That is, the serially connected legs 47 and 45 are unbalanced, while the serially connected legs 49 and 5@ are balanced. The voltage drop across the variable impedance member A1 is now 40 volts while the voltage drop across the lixed impedance member R (leg 4S) is increased to 60 volts. Hence, the voltage drop across the relay winding 622 is now l() volts. By forming the relay til to require a voltage drop for energization greater than attained by partial unbalance of the bridge circuit, ie., more than l0 volts, the unbalance in FlG. 6 is insuthcient to actuate the relay (il, so that the relay contacts are stili maintained in their open positions.

FlG. 7A is somewhat similar to FG. 6A but shows the reverse condition. That is, the recess S? in shaft 22 is disposed in registry with its associated variable imped ance member A2 while the shaft 5S is out of registry with its associated variable impedance member A1. As shown in FlG. 7, the unbalance now occurs in the serially connected legs t9 and 5t?, with a drop of 40 volts across variable impedance member A2 and a 60 volt drop across the impedance member R (leg e9). Here again, the voltage drop across the relay coil 62 is l0 volts and is inadequate to actuate the relay 6l.

l'n FEG. 8A the two shafts i3 and Z2 are disposed in an in-phase condition and with their recesses 58 and 59 envases disposed in alignment with their associated variable impedance members A1 and A2, respectively. By referring to FIG. 8, it will be seen that the upper serially connected legs i7 and 48 are now unbalanced in one direc tion, while the lower serially connected legs 49 and dil are unbalanced in the opposite direction, thereby providing a voltage drop across the relay coil 63 of 20 volts or double that shown in FlGS. 6 and 7. Since the relay 6l is arranged to be actuated at a potential of more than 10 volts, the 20 volt drop across the relay coil o2 is suficicient to actuate the magnetic core member dri and its associated bridging contacts ed to 7l inclusive, thereby completing the circuits through the circuit breakers 38 and 42, the lamp ed and the relay 76.

The circuit breakers 33 and 42, preferably are of the type which lock in upon energization and remain in tl.e locked in position until tripped. Accordingly, the circuit breakers 38 and 42 are jointly actuated to complete the circuits yfrom the DC. ge erators 36 and rl to the iield coils 24 and 2li of the generators and l2, respectively. As previously explained, since the field coils and Zd are jointly excited when the rotors ZTL and l? of the two generators are in proper phase relationship to assume such energization, the two generators l5 and l2 are thus electrically interlocked and may be jointly brought up to speed, after disengagement of the turning gcar mechanisms 26 and 28, by subsequent admission of motive steam to the turbines lll and ld. As well understood in the art, after the two generators are thus electrically syn- .chronized their speeds will be identical regardless of the variations in the electrical loads that they provide (not shown).

During the initial acceleration of tne generators, the recesses 5S and 59 concomitantly sweep into and out of alignment with their associated variable impedance members A1 and A2. Hence the bridge do is alternately balanced and unbalanced .during every revolution of the shafts, thus alternately energizing and deenergizing the relay 6l. This specilic manner of operation has no elect on the circuit breakers 33 and 42, since they lock in as previously described. However, the signal lamp ldis alternately energized and deenergized to visually indicate that the two shafts are being jointly rotated in the inphase condition.

The computer device 63 typically requires a signal of longer duration than the circuit breakers 38 and for well known reasons. However, the relay 76 is energized by the momentary engagement of the relay contacts 7l and '75 and moves its bridging contacts lill and S2 into engagement with their associated stationary contacts 3 and S4, respectively. When the contacts dl and S3 are in engagement with each other, a secondary circuit across the power lines L1, L2 is completed through conductors 89 and 85 establishing a parallel or holding circuit through Ithe winding 77 which is effective to thereafter maintain the relay 76 in the energized position, even though the circuit through the relay contacts 7l and 75' is interrupted. Hence, the contacts El?. and Sd, completing the circuit :through the computer 63, are maintained in the circuit making position for as long a period as required. When it is desired to terminate the circuit through the computer 63, the holding circuit through the relay 'd may be interrupted by moving a suitable manually operated switch 94 lin conductor S9 to the olic position, thereby deenergizing the relay winding 77 and permitting the bridging contacts 8l and 82 to move out of contact with their associated stationary contacts. Subsequent thereto, the bridge circuit 46 may be deenergized by moving the switch 56 to the oil position.

Since the variable impedance members A1 and A2 in the embodiment described above are disposed at 12 oclock, the bridge circuit 46 is ellective to detect the inphase relationship between the two shafts i8 and 22 when the in-phase relationship occurs at l2 oclock (the time that the two recesses 5d and 59 are disposed in alignment with their respective variable imper ance members A1 and A2). However, since the two sharts ld and 22 are rotated at slow but different speeds by the turning gear mechanisms 2.6 and 23, respectively, the iii-phase relationship of the two shafts may momentarily be first obtained at other clock positions, i.e., when the two recesses are not disposed in alignment with their associated variable impedance members. A considerable period of time may thus elapse before the inphase condition can be detected by the bridge circuit 46.

9 to l3 inclusive show a second embodiment of the invention in which the iii-phase relationship of the two shafts may be detected at a plurality of predetermined clock positions.

Referring riov. specifically to FFSS. 9 and l0, there is shown an arrangement including a plurality of variable impedance members A1, B1, C1 and D1, arranged in an array about the periphery of a rotatable shaft ll and disposed at l2, 3, 6 and 9 oclock, respectively. An equal plurality ot tired reference impedance members R, peripherally spaced about the shaft at the same clock locations, are also enployed. ln a similar manner, an equal plurality of variable impedance members A2, B2, C2 and D2 are disposed in an annular array about a rotatable shaft i122. Also, an equal plurality of lined reference impedance members R are disposed in an annular array about the shaft at the saine clock locations.

As shown in FIG. l2, the Variable impedance members A1 and A2, together with their associated reference impedance members R `are connected into a bridge "lf-i6 which may be substantially' identical with the bridge i6 described in connection with the first embodiment and having the winding 162 of a relay ldll interposed therein. The variable impedance members B1 and B2, together with their associated reference impedance members R are connected in a bridge circuit similar to the bridge circuit lo of the rst embodiment and having the winding 262 of a relay Zbl interposed therein (see HG. 13

The shafts lll?) and l2?. may be similar to the shafts l and 22, respectively, described in connection with the tirst embodiment. However, in this embodiment the shafts ll@ and IlfLZ are provided with raised projections or ribs ldd and lda, respectively, instead of the recesses 53 and 59 ot the rst embodiment. rEhe projections ll and 1459, are employed to change the length of the air gaps 21.93 defined by the variable impedance members A1, E1, C1 and D1, and thereby to vary the impedance of these members. However, with this arrangement, when the projection 1.58 is disposed in alignment with one of its associated variable impedance members, such as member B1 (as illustrated in PEG. 9), the length of the air gaps i932 is decreased. l-lere again, although the impedance members may be of either the capacitive or inductive types, they have been ill istrated as being of the inductivo type. Hence, with decrease in the air gaps the magnetic reluctance of the magnetic circuit is decreased with concomitant increase in the inductive impedance of the associated variable impedance member and an increase in voltage drop thereacross.

The bridges lilo and 24d are normally balanced. Representative balanced voltage drop values during the balanced conditions are illustrated in FlG. l2 in conjunction with the bridge M5. lt will be noted that the voltage drop across the relay winding lo?. is zero. However, when the two shafts lll'l and 122 are disposed in a predetermined in-phase rotative position, for example, at 3 oclock as illustrated in FIG. 9, the bridge having the associated impedance members is momentarily unbalanced in the same manner as the first embodiment. FlG. 13 illustrates representative unbalanced Voltage drop values attained at this time. Under such conditions, the voltage drop through the relay winding 262 is suiiicient to actuate the associated relay Zdl.

rl`he variable impedance members C1, C2 and their associated reference impedance members R; and the variars/spas 9 able impedance members D1, D2 and their associated ref` erence impedance members R, are interposed in bridge circuits (not shown) similar to bridge circuits .1.46 and 246, and having relays 361i and dell, respectively, interposed therein (see FG. ll).

With this arrangement it is possible to detect the in phase relation of the two shafts when the projections 7.53 and 159 are disposed at 6, 9 and l2 oclock, in addition to the 3 oclock position shown. Hence, the iii-phase condition of the two shafts may be detected by one of the four bridge circuits in a considerably shorter period of time than the single bridge circuit d6 shown in the hrs embodiment.

As illustrated in FIG. ll, the relays loll, 246i, 361 and alii may be substantially identical to each other and to the relay di previously described in connection with the lirst embodiment, and are actuated by their associated relay windings 162, 262, 362 and 462, respectively. The relay 2st is illustrated in the energized position, while the other relays are illustrated in the deenergzed positions.

The relay tdi is provided with an actuating rod M7 carrying bridging contacts 16S, 169, 17@ and l'l arranged to engage sets of associated stationary contacts 172, 173, lip/'4t and 175.

ln a similar' manner, the relay 263i is provided with a plurality of bridging contacts 26S, 2o?, 27@ and 271 carried by an actuating rod 267 and cooperatively associated with stationary contacts 272, 273, 274 and 275, respectively.

The remaining relays :loll and itil are also provided with contact structure similar to that of relays loll and 261 described above. A conductor @5 is employed to connect the left-hand stationary contacts (such as 172 and 272) to the power supply line L1, while a conductor E9e is provided for connecting the right-hand stationary contacts (such as 172 and 272) to the power supply line L2. In a similar manner, a pair of conductors i797 and ll are employed to connect the lefbhand contacts 173 and 273 to the line L1 and the rightshand contacts 173 and 273 to the line L2, respectively. A pair of conductors 199 and 2li@ are employed to connect the contacts i174 and 274, and a pair of conductors 2M and 2ll2 are employed to connect the contacts E75 and .475, respectively, to power supply lines L1 and L2 in a similar manner.

With the above arrangement, when the bridge circuit 24o is unbalanced by the variation in impedance of the associated impedance members B1 and B2, due to the inphase rotative positions of shafts lid and 122, the relay winding 252 is energized to actuate the actuator rod 267. Accordingly, the bridging contacts 268, 269, 270 and 271i are moved into engagement with their associated stationary contacts and the following circuits are attained across lines L1 and L2:

(l) Circuit breaker 38, conductor 19S, stationary contacts 272, bridging contact 263 and conductor lilo.

(2) Circuit breaker 42, conductor 97, stationary contacts 273, bridging contact 269 and conductor 198.

(3) Signal lamp 64, conductor lill?, stationary contacts 274, bridgingr contact 27h and conductor 20d.

(4) Computer 63, conductor 2M, stationary contacts 275, bridging contact 271 and conductor 262.

From the above, it will be seen that when the two shafts 118 and 122 are in the in-phase condition with their projections 3.58 and 159 disposed at 3 oclock, the relay 216i. is effective to jointly connect the DC. generators 3d and fill (FIG. l) to the generator field windings 24 and 2li, respectively. The relays lol, 363i and lol remain in the deenergized positions, as illustrated in PEG. ll.

Should the two shafts lith and 122 assume an iii-phase rotative position with their projections ldd and l5@ at l2 oclock, the bridge circuit M6 is unbalanced in the same manner as bridge circuit 246 above. Hence, the relay 261 will be deenergized and its actuator rod 267 will drop to the contact disengaging position, while the relay l@ lldl is energized and its actuator rod l67 will be moved upwardly to its Contact engaging position. Under these conditions, the following circuits are completed across lines L1, L2:

(l) Circuit breaker 35, conductor i953', stationary contacts 172, bridging contact led, and conductor 196.

(2) Circuit breaker d2, conductor N7, stationary contacts lift, bridging Contact T169 and conductor 193.

(3) Signal lamp dd, conductor 199, stationary contacts 7.74, bridging contact i7@ and conductor Zilli.

(4) Computer o3, conductor Zilli, stationary contacts l75, bridging contact 177i and conductor 202.

In the event that the shafts MS and M2 attain an inphase condition with their projections ll and X59 disposed at 9 oclock, the relay 361 is energized to complete the circuits through the circuit breakers 3S and 2, the signal lamp dal and the computer 63, while in the event that the insphase condition is obtained at 6 oclock, the relay lol is actuated to complete the above circuits.

In this embodiment, the circuit to computer 63 has been simplified for clarity. However, it must be understood that if it is desired to maintain the circuit to the computer d3 after disengagement of the various relay contacts, a holding relay arrangement, similar to the relay 7d described previously and shown in FlG. Il, may be employed.

lt will now be seen that the invention provides an arrangement for automatically sensing the iii-phase relationship of a pair of rotatable shafts and for automatically initiating a subsequent control function.

lt will further be seen that the invention provides an arrangement for automatically detecting the in-phase relationship of two turbinegenerator rotors and for automatically connecting the DC. power supply to the held coils oi the generators in a simple, yet highly reliable manner. ln addition thereto, the invention provides a control system having means for detecting the irl-phase condition of two slowly rotating shafts and for automatically initiating a plurality of subsequent and related func* tions incidental to proper operation of an electrical power plant.

Although the invention is highly advantageous for automatically detecting the iii-phase relationship of two turbine-generator rotors and for initiating the iield excitation thereof, the invention may be employed for detecting the iii-phase relationship of rotatable shafts of other rotatable apparatus and permits automation of many functions that herletoiore have been manually detected and/or contro ed.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

l. In combination, a rst rotatable shaft and a second rotatable shaft, a single balanced electrical bridge circuit having a first pair of serially connected legs and a second pair of serially connected legs, means interconnected between said rst pair of legs and said second pair of legs for sensing the condition of balance and unbalance in said bridge circuit, means provided on said rst and second shafts for unbalancing said bridge circuit when said first and second shafts are disposed in the same rotative positions, and said sensing means including an electric relay for sensing the unbalance in said bridge circuit when said shafts are in the same rotative positions.

2. In combination,

a first rotatable shaft and a second rotatable shaft,

a balanced electrical bridge circuit having a iirst pair of serially connected legs and a second pair of serially connected legs7 means interconnected between said pair of legs and said second pair of legs for sensing the condition of balance and imbalance in said bridge circuit, and

means provided on said iirst and second shafts for l l unbalancing said bridge circuit when said lirstV and second shafts are disposed in the same rotative pos"- tions, said unbalancing means on the iirst shaft being effective to imbalance said first pair of legs in one direction,

said unbalancing means on the second shaft being etlective to unbalance said second pair of legs in the opposite direction, and

said sensing means being eiiective to sense the joint unbalance of both said pairs of legs and ineffective to sense the unbalance ot only one ot said pairs of legs.

3. In combination, a lirst rotatable shaft and a second rotatable shaft, a balanced electrical bridge circuit having a tirst pair of serially connected legs and a second pair of serially connected legs, a iirst impedance member disposed in one of said first pair of legs, a second impedance member disposed in one of s.fl second pair of legs, means interconnected between said rst pair of legs and said second pair oi legs for sensing the condition of balance and unbalance in said bridge circuit, said lirst and second impedance members being disposed in spaced cooperative relation with said first and second shafts, respectively, and means provided on said iirst and second shafts for jointly varying the impedance of said lirst and second impedance members when said first and second shafts are disposed in the same rotative positions, whereby said bridge circuit is unbalanced.

4. in combination,

first rotatable shaft and a second rotatable shaft, balanced electrical bridge circuit having a first pair of serially connected legs and a second pair orr serially connected legs,

a rst impedance member disposed in one ot said iirst pair of legs,

a second impedance member disposed in one of said second pair of legs, means interconnected between said first pair of legs and said second pair or legs for sensing the condition of balance and unbalance in said bridge circuit,

said rst and second impedance members being disposed in spaced relation with said iirst and second shafts, respectively, and

means provided on said rst and second shafts for jointly varying the impedance of said rst and second impedance members when said lirst and second shafts are disposed in the same rotative positions, whereby said bridge circuit is unbalanced,

said iirst impedance member being disposed in the leg to the left of the serial connection and said second impedance member being disposed in the leg to the right ot the serial connection, whereby When both pairs of legs are jointly unbalanced the Voltage drop across said sensing means is twice the value attained when the iirst and second pairs ot legs are individually unbalanced, and

said sensing means being ineliective to sense the individual unbalance of said pairs of legs.

5. The combina-tion recited in claim 3 and further including a first A.C. generator having a irst rotor and a eld Winding, a second AC. generator having a second rotor and a field winding, said lirst and second rotors being attached to said irst and second shafts, respectively, means including la supply of D.C. current for energizing said iield windings, means for individually driving said rotors at different slow speeds, and means actuated by the bridge imbalance sensing means for jointly connecting said DC. supply to said field windings When said shafts are disposed in the same rotative positions.

6. A device for sensing the irl-phase relationship of a lirst rotating shaft and a second rotating shaft in a plurality of predetermined rotative positions, comprising a plurality of AC. bridge circuits, each or said bridge circuits having suostantially identical electrical characterl2; istics and including four leus, electrical impedance members disposed one in each of said legs and forming lirst and second pairs, the impedance ratio of said irst pair of impedance members being equal to the impedance ratio of said second pair of impedance members, whereby all of said bridge circuits are electrically balanced, said tirst pair of impedance members including a tirst reference impedance member and a first variable impedance member connected in series and disposed in radially spaced relation with the periphery of said rst shaft, said second pair of impedance members including a second reference impedance member and a second variable impedance member connected in series and disposed in radidly spaced relation with the periphery of said second shaft, all of said lirst variable impedance members and said second variable impedance members being correspondingly peripherally spaced around their associated shafts, first means on said iirst shaft for successively varying the impedance of said irst variable impedance members as said first shaft is rotated, second means on said second shaft for successively varying the impedance of said second variable impedance members, as said second shaft is rotated, said rst and second impedance varying means being effective to jointly vary the impedance oi said rirst and second variable impedance members in at least one of said bridge circuits when said shafts are disposed in phase with each other in one of said predetermined rotative positions, thereby unbalancing said one bridge circuit, `and means responsive to the imbalance of said one bridge circuit for sensing the iii-phase relationship of said shafts.

7. In combination, a first rotating shaft and a second rotating shaft, a device for sensing the iii-phase relationship of said shafts in a plurality ot predetermined rotative positions comprising, a plurality of AC. bridge circuits each or said bridge circuits having substantially identical electrical characteristics and including first and second serially connected legs, third and fourth serially connected legs, of electrical impedance members disposed one in each of said legs and forming first and second pairs, the impedance ratio of said irst pair of impedance members being unity and the impedance ratio of said second pair of impedance members being unity, whereby all of said bridge circuits are electrically balanced and the individual voltage drops across each of said iirst pair of impedance members are equal and the individual voltage drops across each of said second pair of impedance members are equal, said lirst pair of impedance members including a lirst reference impedance member and a first variable impedance member disposed in radially spaced relation with the periphery of said first shaft, said second pair of impedance members including a second reference impedance member and a second Variable impedance member disposed in radially spaced relation with the periphery of said second shaft, all of said first variable impedance members and said second variable impedance members being correspondingly peripherally spaced around their associated shafts, lirst means on said first shaft for successively varying the impedance ot each of said irst variable impedance members and unbalancing the voltage drops across said lirst and second legs in one direction,y second means on said second shaft for successively varying the impedance of each of said second variable impedance members and unbalancing the voltage drops across said third and fourth legs in the opposite direction, said first and second impedance varying means being etlective to jointly vary the impedance of said Iirst and second variable impedance members in at least one of said bridge circuits when said shafts are disposed in phase with each other in one of said predetermined rotative positions, thereby unbalancing the voltage drops in said one bridge circuit in opposite directions, means interconnected between the midpoints of said iirst and second legs and said third and fourth legs, said last mentioned means being responsive to the imbalance of said voltage drops in air/aces 13 said one bridge circuit in opposite directions and sensing the in-phase relationship of said shafts, and means actuated by said voltage drop sensing means for interlocking said shafts for in-phase rotation.

8. in combination, a first A.C. generator having a rotor and a field winding, a second A.C. generator having a rotor and a field winding, means including a supply of D.C. current for energizing said field windings, means for driving said rotors at slow speeds, a balanced electrical bridge circuit having a first pair of serially connected legs and a second pair of serially connected legs, means interconnected between said first pair of legs and said second pair of legs for sensing the condition of unbalance in said bridge circuit, means associated with said first and second rotors for unbalancing said bridge circuit when said first and second rotors are disposed in the same rotative positions, and means actuated by said sensing means for concomitantly connecting said DC. current supply to said field windings when said bridge circuit is unbalanced.

9. A device for sensing an in-phase rotative relationship of a first rotating shaft and second rotating shaft, comprising an A.C. bridge circuit having four legs, electrical impedance members disposed one in each of said legs and forming first and second pairs, the impedance ratios of said pairs of impedance members being equal, whereby said bridge circuit is electrically balanced, said first pair of impedance members being disposed in spaced relation with the periphery of said first shaft and said second pair of impedance members being disposed in spaced relation With the periphery of said second shaft, first means on said first shaft for varying the impedance of one of said first pair of impedance members, as it sweeps past said one of said first pair of impedance members, second means on said second shaft for varying the impedance of one of said second pair of irnpedance members as it sweeps past said one of said second pair of impedance members, said first and second impedance varying means being effective to jointly vary the impedance of their associated impedance members when the shafts are disposed in the same rotative positions with relation to each other, whereby said bridge is momentarily electrically unbalanced, and means responsive to the unbalance in said bridge for sensing the inphase rotative position relationship of said shafts.

l0. In combination, a first rotating shaft and a second rotating shaft, a device for sensing an irl-phase rottativte relationship of said shafts comprising an AiC. bridge circuit having four legs, electrical inductive impedance members disposed one in each of said legs and forming first and second pairs, the impedance ratios of said pairs of impedance members being equal, whereby said bridge circuit is electrically balanced, said first pair of impedance members being disposed in spaced relationship with the periphery of said first shaft and each forming a magnetic circuit therewith, said second pair of impedance members being disposed in spaced relation with said second shaft and each forming a magnetic circuit therewith, first means on said first shaft for varying the inductance of one of said first pair of impedance members, as it sweeps past said one of said first pair of impedance members, second means on said second shaft for varying the inductance of one of said second pair of impedance members as it sweeps past said one of said second pair of impedance members, said first and second inductance varying means being effective to jointly lvary the inductance of their associated impedance members when the shafts are disposed in an irl-phase position, whereby the impedance ratios of both said pairs of impedance members are rendered unequal and said bridge is electrically unbalanced, means responsive to the unbalance in said bridge for sensing the in-phasc relationship of said shafts, and means actuated by said sensing means for initiating a subsequent control function.

References Cited by the Examiner UNITED STATES PATENTS 1,890,891 12/32 Vopel et al. 340-268 X 2,493,028 1/50 Putt 324--70 X 2,731,599 1/56 Groeper 324--70 2,828,481 3/59 Latapie 340-268 2,943,307 6/60 Sampson 317-6 X SAMUEL BERNSTEiN, Primary Examiner, 

1. IN COMBINATION, A FIRST ROTATABLE SHAFT AND A SECOND ROTATALE SHAFT, A SINGLE BALANCED ELECTRICAL BRIDGE CIRCUIT HAVING A FIRST PAIR OF SERIALLY CONNECTED LEGS AND A SECOND PAIR OF SERIALLY CONNECTED LEGS, MEANS INTERCONNECTED BETWEEN SAID FIRST PAIR OF LEGS AND SAID SECOND PAIR OF LEGS FOR SENSING THE CONDITION OF BALANCE AND UNBALANCE IN SAID BRIDGE CIRCUIT, MEANS PROVIDED ON SAID FIRST AND SECOND SHAFTS FOR UNBALANCING SAID BRIDGE CIRCUIT WHEN SAID FIRST AND SECOND SHAFTS ARE DISPOSED IN THE SAME ROTATIVE POSITIONS, AND SAID SENSING MEANS INCLUDING AN ELECTRIC RELAY FOR SENSING THE UNBALANCE IN SAID BRIDGE CIRCUIT WHEN SAID SHAFTS ARE IN THE SAME ROTATIVE POSITIONS. 